Many of today's power transmissions, especially multi-speed automatic shifting power transmissions, have one or more one-way torque-transmitting devices commonly called one-way clutches. The engineering community provides the nomenclature of one-way clutch whether the one-way device is a holding or retarding device or a rotational transmitting device. The terminology of one-way torque transmitter and one-way clutch will both be used in this description.
As a general rule, the one-way clutch has one direction of operation for performing the torque-transmitting function and in the other direction of operation permits free rotation between the two members, which are connected with the one-way device. If the torque transmitter is either employed as a brake or retarding device, one of the races, generally the outer race of the one-way clutch is held stationary by a portion of the transmission housing. The other race or generally inner race of the torque-transmitting one-way clutch is connected with a gear element within the transmission.
When the gear element attempts to rotate in one direction, the one-way clutch will lock-up between the gear member and the transmission housing thereby holding the gear member stationary such that a ratio is established within the transmission. When the gear member is driven or rotated in the opposite direction, the one-way clutch permits free rotation between the inner and outer races such that the gear connected therewith is free to rotate relative to the meshing members.
There has been a number of proposals for one-way clutches wherein an actuator mechanism is provided to cause the one-way clutch to be energized in one direction of operation during a portion of the torque-transmitting function and upon actuation of the control mechanism or actuator, the one-way device is operable to be able to transmit torque in the opposite direction of rotation.
Generally, with these devices, the actuating mechanism is either an electrical mechanism or a friction mechanism, which is disposed in series with the one-way torque transmitter. The friction mechanism is generally disposed between the outer race of the one-way torque transmitter and the transmission member to which it is to be connected, generally the transmission housing. However, in most applications of one-way torque transmitters or one-way clutches, the one-way device is fixed within the system to operate in one direction of rotation only.
The design of the one-way clutch has many forms. The one-way clutch may be a roller type, a sprag type, or what is commonly termed a diode type of mechanism. Each of these various mechanical elements within a one-way clutch provides identical functions and can be interchanged without significant design problems.